Yanmar 3TNM74F Troubleshooting
| Engine Model: Yanmar 3TNM74F |
| Engine Type: 4-cycle vertical 3-cylinder indirect injection liquid-cooled diesel |
| Total Displacement: 60.6 cu.in (0.99 L) |
| Rated Engine Power: 21.6 Hp (16 kW) at 3600 rpm |
| Aspiration Type: Naturally aspirated |
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| Engine difficult to start or doesn't start |
Fuel filter plugged - Filter maintenance required.
Air trapped in fuel system - Bleed air.
Clogged or defective injection nozzles - Test injection nozzles and change if necessary.
Fuel injection pump malfunction - Replacement or repair required.
Valve timing is incorrect - Adjust or change timing gear.
Clogged fuel pipes - Clean or change fuel pipes.
Unadjusted injection timing - Set up as recommended.
Worn piston rings and cylinder - Change faulty parts.
| Diesel starts but stalls immediately |
Fuel filter element is clogged - Replace the filter element.
Fuel injection pump is damaged - Repair or change injection pump.
Air filter clogged - Air filter maintenance required.
Nozzle opening pressure is not adjusted - Set it correctly.
| Engine stalls during operation |
Improper setting of fuel injection pump timing - Check the fuel injection pump timing adjustment.
Clogged fuel filter - Change filter element.
Coolant temperature is low - Warm up the engine.
Stuck or burnt injection nozzle - Service or change injection nozzles.
Too low idle RPM - Correct the settings.
Excessive valve clearance - Check and adjust.
Fuel injection pump malfunctioning - Change or repair the pump.
| Engine power is insufficient |
Dirty or damaged injection nozzles - Install a new kit of correctly balanced nozzles.
Dirt in the fuel lines or hoses - Service fuel hoses and lines.
Air filter clogged - Replace air filter element.
Blown cylinder head gasket - Gasket should be replaced.
Unadjusted injection timing - Set up as recommended.
Fuel injection pump is defective - Replacement or repair required.
One of moving engine components is worn - Repair or replace defective components.
Dirty radiator fins or defective radiator cap - Install new cap or clean radiator.
Engine coolant is insufficient - Fill radiator to proper level and check components for faults.
Broken or loose fan belt - Change the fan belt.
Insufficient engine oil - Check and refill engine oil.
Blown cylinder head gasket - Change cylinder head gasket.
Injection timing is wrong - Set the injection timing correctly.
Insufficient engine oil - Add oil as required.
Oil pump malfunction - Check and replace if necessary.
Clogged oil filter - Service or replace engine oil filter.
Relief valve is stuck or worn - Change or clean relief valve.
Clearance of crankshaft bearing is excessive - Inspect and replace or repair faulty parts.
Excessive oil clearance of crankpin bearing - Test and repair or replace worn parts.
| Excessive engine oil consumption |
Oil leakage: Worn seals or gaskets - Replace to repair leaks.
Oil viscosity is wrong - Use correct viscosity oil.
Stuck or defective piston rings - Replace piston rings.
Valve stems and guides are worn - Replace defective valves.
Cylinder liners or pistons are damaged - Check pistons and liners, replace as required.
| Abnormal engine noise or knocking |
Low coolant temperature - Warm up engine as required.
Low engine oil level - Check oil level and add oil as required.
Timing of fuel injection pump is incorrect - Adjust as recommended.
Worn or scored pistons - Pistons replacement required.
Connecting rod is defective or not aligned - Align or change connecting rod.
| Starter motor cranks slow |
Low battery capacity - Battery is drained, charge it.
Battery does not hold charge - Service charging system or install new battery.
Battery terminals are corroded or wires are disconnected - Check battery wires and service or replace terminals.
Battery is discharged or defective - Charge or change the battery.
Wiring is improperly connected or disconnected - Check wiring and connect properly.
Battery capacity is low - Recharge the battery.
Starter motor failure - Change or repair starter.
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